Various kinds of discharge electrodes are known to the art, and can normally be classified under two separate groups.
The discharge electrodes of the first category or group comprise rods or thin metal strips attached to a frame structure, to which the voltage source is connected. The rods are arranged parallel with one another and are mounted between mutually opposite parts of the frame structure, these rods normally extending in a helical configuration or having the form of weight-loaded straight rods.
Also known to the art are discharge electrodes which are punched from thin sheet-metal material to form therein pointed parts which are each bent to a respective one side of the centre line of the electrode, so as to form electrode parts and electrode tips.
Similarly to the aforedescribed rods, these constructions are not self-supporting, but are secured in a frame structure.
It is necessary with this group of electrodes to restrict the length of the rod or the plate material, and it is necessary to construct a plurality of such frames one upon the other, in order to obtain a sufficiently high structure.
The upper part of the frame structure is normally held by carrier means.
The other category or group of discharge electrodes are designated "rigid discharge electrodes" and are, in themselves self-supporting. These electrodes comprise an elongated member having attached thereto a plurality of electrode parts which present one or more discharge electrode tips. These electrode parts are distributed along the rod-like member and extend beyond the outer defining surfaces thereof. A rigid or self-supporting discharge electrode of this kind is fastened at the top thereof to a carrier and is guided in its bottom region in a manner such to prevent the electrode from deviating from a predetermined intended position.
The discharge electrode described and illustrated in UK Patent Specification No. 1 100 328 constitutes an example of such prior art discharge electrodes.
Another example of a prior art discharge electrode is illustrated in the German Offenlegungsschrift No. 1 557 148.
In this publication it is shown a discharge electrode intended for use in an electrostatic dust separator which, in addition to the discharge electrode, also incorporates one or more collector electrodes and a voltage source intended for supplyin9 energy to the discharge and collector electrodes so as to create therebetween a high d.c. voltage and an electric field effective to separate dust from a dust-laden medium passing through the precipitator or dust separator. This dust is collecting primarily on the collector electrodes.
In the prior art the shown discharge electrode comprising an elongated member having distributed therealong a plurality spaced apart of electrode parts, which presents one or more discharge tips and which extend transversally to the longitudinal axis of the elongated member.
This elongated member being formed from a folded material or a similarly corrugated metal sheet. The folds are oriented in the longitudinal direction of the elongated member.
Finally it should be mentioned that still other constructions are known in previously printed publications and as an example of such constructions reference is given to the following publications:
U.S. Pat. No. 4,303,418 PA1 U.S. Pat. No. 4,115,083 PA1 Swedish Patent Specification No. 385 548 and PA1 France Patent Specification No. 2 004 430.